Coordinated 1,3-Diyne Diols as Organometallic Building Blocks for Large Macrocycles Containing Oxygen and Unsaturated Donor Units

The acid-catalysed reaction of [(Co 2 (CO) 6 (μ-η 2 -HOCH 2 C 2 -)} 2 ] (la) with a range of alkyl diols has been examined as means of preparing large crown-type macrocycles (up to twenty eightmembered) containing at least one coordinated 1,3-diyne unit, multiple oxygen atoms and a variety of soft donor units. Thus, interaction of la with HOCH 2 (CH 2 ) n CH 2 OH, allows access to the monomeric cyclised complexes [(Co 2 (CO) 6 } 2 {cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 ΟCH 2 (CH 2 ) n CH 2 Ο)] (3a: n = 2, 3b: n = 3,3c: n = 4) along with the dimeric cyclised species [{Co 2 (CO) 6 } 2 -(cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 OCH 2 (CH 2 ) n CH 2 O}] 2 (4a: n = 2, 4b: n = 3, 4c: n = 4). Introduction of additional oxygen donor atoms into the macrocycle can be achieved by reaction of la with the glycols, HO(CH 2 CH 2 O) n H, to afford exclusively monomeric [{Co 2 (CO) 6 } 2 {cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 O(CH 2 -CH 2 O) n }] (5a: n = 3, 5b: n = 4). On the other hand, treatment of la with the 1,3-diyne-linked alkyl diols, HOCR 2 C≡CC≡ CCR 2 OH, furnishes the more rigid monomeric [{Co 2 (CO) 6 } 2 -(cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 ΟCR 2 C 2 C 2 CR 2 Ο)] [6a: R = H, 6b: R = Me] and dimeric macrocycles [(Co 2 (CO) 6 } 2 {cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 ΟCR 2 C 2 C 2 CR 2 Ο}] 2 [7a: R = H, 7b: R = Me], whereas the use of the alkynyl- or aryl-linked alkyl diols, HOCH 2 (L)CH 2 OH, affords the unsymmetrical dimeric [{Co 2 -(CO) 6 } 2 {cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 } 2 O{OCH 2 (L)CH 2 O}] [8a: L = -C≡C-, 8b: L = 1,4-C 6 H 4 ) and symmetrical dimeric species [{Co 2 (CO) 6 } 2 {cyclo-μ-η 2 :μ-η 2 -CH2C2C2CH20CH2(L)-CH 2 Ο}] 2 [9a: L = -C≡C-, 9b: L = 1,4-C 6 H 4 ]. Also isolated as a by-product from all the above reactions is the self-dimerised macrocycle [{Co 2 (CO) 6 } 2 {cyclo-μ-η 2 :μ-η 2 -CH 2 C 2 C 2 CH 2 O)] 2 (2) which can itself be synthesised more directly by treating la with catalytic quantities of HBF 4 ·OEt 2 . Single crystal X-ray diffraction studies have been performed on 2, 3a, 5a, 7a, 8a, 8b and 9a.